It is well known to provide a releasable lock of the wheels to the frame of a bicycle. Such a releaseable lock allows easy removal of the wheels themselves, for example for their replacement, for easing the transportation of the bicycle or as an anti-theft measure.
For this purpose, the ends of the branches of the front and rear forks of the frame of bicycles have a housing hole that is open through a slide slit.
When fixing the wheel to the frame, a traction rod extending in an axial through hole of the hub of the wheel is made to slide along the slide slits up to the housing holes at the ends of the branches of the fork. Clamping elements at the ends of the traction rod, projecting outside of the fork, are axially displaced closer to each other. These elements come into an abutment and clamping coupling against the outer surfaces of the branches of the fork, so as to secure the hub of the wheel to the frame. To release the hub, the clamping elements are axially displaced apart from each other, loosening the abutment and clamping coupling and allowing the sliding of the traction rod and therefore of the hub of the wheel outside of the housing holes of the fork.
A first of the clamping elements comprises a nut that can be screwed onto a threading at a first end of the traction rod.
The second of the clamping elements comprises a housing for a rotation cam extending in a hole at the second end of the traction rod, and an actuation lever for driving the rotation of the cam. The housing abuts against the outer surface of the fork on the frame.
Actuating the cam secures the hub to the frame by tensioning the traction rod.
In prior art locking devices, the actuation lever is connected to just one end of the rotation cam.
The Applicant has perceived that in such devices, during the actuation of the actuation lever, the rotation cam is also subjected to a torque with respect to a pivot point located at the end of the rotation cam opposite the end connected to the actuation lever, and that such a torque generates undesired stresses in the pivot point of the cam, which can lead to wearing and breaking of the cam.